Anisotropic AVO

What is it about?

This paper is about a seismic reservoir characterization case study in which velocity anisotropy has significant impact on AVO response. Key findings include: 1. If non-negligible differences in the anisotropy parameters between the various lithologies cause vertical profiles of Vp/Vs and the anisotropy parameters to be dissimilar, a significant mismatch between the anisotropic data and isotropic synthetic seismogram AVO response will occur. 2. This may be the case where volcanic rock is present with shale and sandstone. 3. In this case, the interpretation of the far-angle stack is totally different depending on whether we assume an isotropic or anisotropic medium. Reservoir characterization using the anisotropic elastic impedance is demonstrated.

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Why is it important?

The observations are important because: 1. Routinely applied methods in seismic reservoir characterization (wavelet extraction, AVO analysis, AVO inversion etc.) usually assume that the earth can be modeled by a stack of isotropic layers. 2. Shale constitutes most of the overburden in conventional oil and gas fields worldwide, and usually has relatively large positive anisotropy parameters due to the alignment and platy habit of its constituent minerals.